Using the KP hierarchy reduction method, we investigate the \(\mathcal{P}\mathcal{T}\) -symmetric nonlocal Maccari system, which serves as a two-dimensional extension of the nonlocal nonlinear Schrödinger equation. A family of exact lump–soliton solutions on a trigonometric periodic line-wave background is constructed in the form of \((2J+1)\times (2J+1)\) Gram-type determinants. Under different parameter restrictions, both normal and anomalous interaction between localized lump waves and line solitons are revealed. Localized energy can propagate elastically through line solitons, exhibiting wave-like behavior, or be annihilated or radiated by line solitons through fusion and fission mechanisms. These results indicate that nonlocal systems not only admit solutions satisfying \(\mathcal{P}\mathcal{T}\) symmetry, but also support various types of interaction processes commonly observed in local systems. Compared with previously reported breather, rogue-wave and lump solutions on nonzero or periodic backgrounds, the present solutions emphasize mixed lump–line-soliton interactions and their asymptotic mechanisms on a trigonometric periodic line-wave background.